feat: add custom headers support for sync providers#1955
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raflFaisal wants to merge 6 commits intoopen-feature:mainfrom
Closed
feat: add custom headers support for sync providers#1955raflFaisal wants to merge 6 commits intoopen-feature:mainfrom
raflFaisal wants to merge 6 commits intoopen-feature:mainfrom
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This pull request introduces the ability to specify custom headers for HTTP and gRPC sync providers, either globally via a new CLI flag and environment variable or per-source in the configuration. The implementation correctly handles header merging and application to outbound requests, including special logic for the HTTP Host header. A compilation error was identified in the unit tests where the NewHTTP function is called with an incorrect number of arguments.
Add --sync-provider-headers CLI flag and per-source headers configuration to inject custom HTTP headers and gRPC metadata into outbound sync requests. This enables use cases like interop gateway routing and tenant identification. Per-source headers take precedence over global headers for conflicting keys. Signed-off-by: raflFaisal <faisal.rafi.mca@gmail.com>
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Signed-off-by: faisal.rafi <faisal.rafi.mca@gmail.com>
Signed-off-by: faisal.rafi <faisal.rafi.mca@gmail.com>
Removed an empty line for cleaner code. Signed-off-by: faisal.rafi <faisal.rafi.mca@gmail.com>
Signed-off-by: faisal.rafi <faisal.rafi.mca@gmail.com>
Signed-off-by: faisal.rafi <faisal.rafi.mca@gmail.com>
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Summary
Add support for custom headers in sync providers (HTTP and gRPC), configurable both globally via CLI flag and per-source in JSON configuration.
Problem
flagd's sync providers cannot inject custom request headers into outbound requests. This limits integration with environments where intermediaries (API gateways, reverse proxies, service meshes) require specific headers for routing, tenant identification, or policy enforcement, resulting in errors like 421 Misdirected Request or misrouting.
Solution
CLI flag: --sync-provider-headers="Key=Value,Key2=Value2" injects headers into sync requests.
Per-source config: "headers": {"Key": "Value"} in the source JSON for fine-grained control.
Per-source values take precedence over global values for conflicting keys.
HTTP:
flagd start --sync-provider-headers="X-Gateway-Host=myhost,X-Tenant-ID=tenant1"
--sources='[{"uri":"http://my-flags.com/flags","provider":"http"}]'
GRPC:
flagd start --sources='[{"uri":"proxy-gateway-server.xyz.com", "provider":"grpc","selector":"features","headers":{"X-Routing-Target-Host":"b.flags-server.service"}}]'
Headers are sent as HTTP request headers for HTTP sync and as gRPC metadata for gRPC sync.
Scope & compatibility
Fully backward compatible, i.e. headers are optional and default to empty
No behavior change for existing configurations
Covers both HTTP and gRPC sync providers